This application claims priority of Taiwan Patent Application Serial No. 091121422 filed on Sep. 19, 2002.
The present invention relates to a projector apparatus, and especially to a projector apparatus with a color wheel for filtering the light beam.
The full color display systems of today generally form images by combining three projected primary colors, namely red, green, and blue, to become a full color image to the eyes of the viewers. Therefore, images are typically formed with three separate optical modules.
The image display systems selectively use spatial light modulators or cathode ray tubes as optical modules. The spatial light modulators provide higher resolution and occupy smaller space than the cathode ray tubes. Digital micro-mirror device is an example of spatial light modulators and is often used in direct-view or projection-type displays.
The digital micro-mirror device consists of hundreds or thousands of micro mirror arrays, and one mirror corresponds to one image pixel. With the aid of digital micro-mirror device array and proper filters, the image display system may form images consisting of three primary colors by single light source. Using light sources and three cathode ray tubes as modulators may also form the images consisting of three primary colors.
The spatial light modulators adopt sequential color filters to form color images. All image pixels are formed by light respectively filtrated by the filters. Such display systems typically use color wheel having red, green, and blue filters as sequential color filter to form full color images. Therefore, light is filtrated by the color wheel to become corresponding colors and projected into the spatial light modulator to form every image pixels.
Typical color wheels are disk-type color wheels with a plurality of filters. However, there are other options, e.g. rotatable drum-type or polygonal color wheel. While projecting into the color wheel, the white light beam is filtrated by the filters to become light beam of one of the three primary colors. The color wheel includes at least one filter for each primary color.
Typically, the rotation speed of the color wheel should be high enough allowing at least one primary color image to create persistence. Color wheels with higher rotation speed or more filters may moderate undesired discontinuity of output image.
The three primary color lights combine to become white light. But such combined white light is not bright enough for data-type images. To this end, color wheels with red, green, blue, and white are devised. However, such color wheel cannot produce film-type images of naturalism.
The U.S. Pat. No. 5,650,832 discloses a method for generating light beams with different brightness and saturation. As shown in FIG. 5, the light beam is adjusted to project into different spots 51, 52, and 53 of the conventional three-color color wheel 500 to generate light beams with different brightness and saturation. However, optical path difference exists between filtrated color light beam and non-filtrated white light beam. Furthermore, the mix-ratio of filtrated color light beam to non-filtrated white light beam is constant as the projection spot is fixed, thus not allowing minor adjustment to meet different needs.
One aspect of the present invention provides a projector apparatus allowing brightness adjustment of output image.
The projector apparatus includes a lamp, a color wheel, a driving device, and a light pipe. The lamp generates the light beam. The color wheel filters the light beam. The driving device is connected to the color wheel and selectively drives the color wheel to rotate, to radially move, or to axially move. The light pipe propagates the light beam.
The color wheel is selectively disk-type or barrel-type and has three, but not limited to three, filter devices. At least one filter device includes a first filter and a white filter connected to the first filter. In one embodiment, the first filters are respectively red, green, and blue filters. A boundary arc is defined at the connection of the first filter and the white filter. Besides, ratio of the area of the first filter to the area of the white filter for each filter device is predetermined, and ratios among the filter devices are selectively the same. The white filter is a transparent filter having the same refraction index as the first filter.
While the driving device drives the color wheel to rotate, the light beam projects into every filter devices sequentially. As the color wheel is a disk-type color wheel, the driving device may drive the color wheel to move radially for allowing the light beam to project into the first filter, the white filter, or onto the boundary arc. As the light beam passes the first filter, the filtrated light beam respectively becomes red, green, or blue light. While passing through the first filter, the white filter, and the boundary arc, the light beam is filtrated simultaneously by the first filter and the white filter. Therefore, the filtrated light beam becomes a combination of white light and red, green, or blue light respectively. Light filtrated this way has higher brightness.
The advantage and spirit of the present invention may be further comprehended through the following detailed description and attached drawings.